1. Field of the Invention
This invention relates to a pulley apparatus with built-in one-way clutch.
2. Description of the Related Art
A pulley apparatus with built-in one-way clutch is fastened to the end of the rotating shaft of an alternator in the generator of an automobile, for example, to drive the alternator by running an endless belt between the drive pulley attached to the end of the engine crankshaft and the pulley apparatus with built-in one-way clutch.
The construction of the alternator, which generates the power required for the automobile using as the drive source the engine for running the automobile, is disclosed for example in Japanese Patent Publication No. Toku Kai Hei 7-139550. FIG. 3 shows the alternator 1 disclosed in this publication. This alternator 1 comprises a housing 2, and rotating shaft 3 on the inside of the housing 2. The rotating shaft 3 is supported by a pair of rolling bearings 4 such that it rotates freely. There is a rotor 5 and commutator 6 in the middle of the rotating shaft 3. Also, a pulley 7 is fixed to one end (right end in FIG. 3) of the rotating shaft 3 on the section that protrudes to the outside of the housing 2. When installed in an engine, an endless belt is extended around this pulley 7 and the engine crankshaft drives the rotating shaft 3.
Conventionally, a pulley 7 was simply fixed to the rotating shaft 3. However, recently, various kinds of one-way clutch built-in pulleys for alternators have been proposed, wherein when the running speed of the endless belt is constant or increasing, power is freely transmitted from the endless belt to the rotating shaft, and when the running speed of the endless belt is decreasing, the relative rotation between the pulley and the rotating shaft is free, and these pulleys are being used in some applications. For example, a one-way clutch built-in pulley for an alternator as described above has been disclosed in Japanese Patent Publications Nos. Toku Kai Sho 56-101353, Toku Kai Hei 8-226462, Toku Kai Hei 9-229097, Toku Kai Hei 11-22753, Toku Kai Hei 11-159599, Toku Ko Hei 7-72585, and French patent FR2726059A1 etc. Also, this kind of pulley apparatus with built-in one-way clutch for an alternator is actually being used in some applications.
FIG. 4 shows the pulley apparatus with built-in one-way clutch for an alternator that is disclosed in Japanese Patent Publication No. Toku Kai Hei 11-22753. This pulley apparatus with built-in one-way clutch for an alternator has a sleeve 8 that can be fitted over the tip end of the rotating shaft 3 (see FIG. 3) of the alternator 1. In addition, there is a pulley 7 located around this sleeve 8 such that it is concentric with the sleeve 8. There is a pair of support bearings 9 and the one-way clutch 10 located between the outer peripheral surface of the sleeve 8 and the inner peripheral surface of the pulley 7.
The support bearings 9 support radial loads that are applied to the pulley 7, while at the same time make it possible for free relative rotation between the sleeve 8 and pulley 7.
The one-way clutch 10 transmits rotation power from the pulley 7 to the sleeve 8 only when the pulley 7 rotates in a specified direction with respect to the sleeve 8.
The one-way clutch 10 has an inner ring 11 for the one-way clutch that is fitted onto and fixed around the middle section in the axial direction of the sleeve 8. There is a plurality of depressions 12, called ramp sections, are formed at uniform intervals all the way around in the circumferential direction on the outer peripheral surface of the inner ring 11 for the one-way clutch. This outer peripheral surface functions as a cam surface 13. In contrast to this, there is an outer ring 14 that is fitted into and fixed around the inner peripheral surface of pulley 7. The middle section in the axial direction of this outer ring 14 functions as the outer ring for the aforementioned one-way clutch 10. Therefore, the inner peripheral surface of the middle section in the axial direction of the outer ring 14 is simply a cylindrical surface generally along its entire length in the axial direction. The one-way clutch 10 comprises the middle section in the axial direction of the outer ring 14, the inner ring 11 for the one-way clutch and a plurality of rollers 15. The plurality of rollers 15 are supported by a clutch retainer 16 such that they rotate freely and can displace a little in the circumferential direction. In addition, there are springs between the column sections of the clutch retainer 16 and the rollers 15. A cylindrical-shaped space is formed between the outer peripheral surface of the cam surface 13 and the inner peripheral surface in the middle section in the axial direction of the outer ring 14. In the cylindrical-shaped space, the springs elastically press against the rollers 15 in the direction of the section where the width in the radial direction becomes narrow.
On the other hand, outer bearing races 18 for the support bearings 9 are fitted around the inner peripheral surfaces of the sections near both ends in the axial direction of the outer ring 14 that is fitted and fixed around the inner peripheral surface of the pulley 7, and inner bearing races 19 for the support bearings 9 are fitted around the outer peripheral surfaces of the sections on both ends in the axial direction of the sleeve 8. Also, a plurality of rolling elements (balls) 22 are located between the outer-ring raceways 20 that are formed around the inner peripheral surfaces of the outer bearing races 18, and the inner-ring raceways 21 that are formed around the outer peripheral surfaces of the inner bearing races 19.
Moreover, an attachment protrusion 17 protruding radially inward is formed part way around in the circumferential direction on the inner peripheral surface of one end (right end in FIG. 4) in the axial direction of the clutch retainer 16. This attachment protrusion 17 is held between the end surface of the inner ring 11 for the one-way clutch and the end surface of the inner bearing race 18 of one of the support bearings (right bearing in FIG. 4).
The reason for using a pulley apparatus with built-in one-way clutch for an alternator is as follows. There are changes in rotation speed of the engine crankshaft when firing occurs, and in the case of a diesel engine or direct-injection gasoline engine, changes in rotational angular speed of the crankshaft become especially large at low rotational speed such as during idling. As a result, the running speed of the endless belt 23 that extends around the drive pulley that is fastened to the end of the crankshaft also changes small. On the other hand, the rotating shaft 3 of the alternator 1 is rotated and driven by the endless belt 23 by way of the pulley 7, and there is no sudden change due to the inertial mass of the rotating shaft 3 and the rotor 5 and commutator 6 (see FIG. 3) that are fastened to the rotating shaft 3. Therefore, when the pulley 7 is simply fastened to the rotating shaft 3, the number of revolution of the rotating shaft 3 decreases as is when the running speed of the belt drops, so that the generating efficiency of the alternator decreases. At the same time, there is a tendency for rubbing in both directions between the endless belt 23 and the pulley 7 due to the change in the rotational angular speed of the crankshaft.
As a result, stress that repeatedly changes direction acts on the endless belt 23 that it rubs with the pulley 7, and thus slipping occurs easily between this endless belt 23 and pulley 7, or causes the life of the endless belt 23 to be shortened.
Moreover, the drop in the generating efficiency of the alternator 1 described above, and the decrease in life of the endless belt 23 due to friction between the outer peripheral surface of the pulley 7 and the inner peripheral surface of the endless belt 23 are also caused by repeatedly accelerating or decelerating during operation. In other words, during acceleration, the drive force is transmitted from the endless belt 23 to the pulley 7, and during deceleration the endless belt 23 applies a braking force on the pulley 7 that tries to continue rotating due to inertia. Not only does the generation efficiency decrease due to this braking force, but this braking force and the drive force act as an opposite direction friction force on the inner peripheral surface of the endless belt 23, and therefore decreases the life of the endless belt 23.
Particularly, in the case of a vehicle equipped with an exhaust brake, the deceleration that slows the rotation of the crankshaft when acceleration is off becomes large, and the friction force that is applied to the inner peripheral surface of the endless belt 23 due to the braking force becomes large, so as a result there is a large decrease in generating efficiency and life.
Here, a pulley apparatus with built-in one-way clutch is used as the pulley 7 described above. There is a cylindrical space formed between the outer peripheral surface of the inner ring 11 for the one-way clutch and the inner peripheral surface in the middle section in the axial direction of the outer ring 14. When the running speed of the endless belt 23 is constant or increasing, the rollers 15 of the one-way clutch 10 bite into the section of the cylindrical space where the width in the radial direction becomes narrow, or in other words, they become locked such that rotating power can be freely transmitted from the pulley 7 to the rotating shaft 3. Conversely, when the running speed of the endless belt 23 decreases, the rollers 15 move into the section of the cylindrical space where the width is large such that they can rotate freely, or in other words, they are in the overrun state such that the pulley 7 rotates freely with respect to the rotating shaft 3.
In other words, when the running speed of the endless belt 23 is decreasing, the rotational angular speed of the pulley 7 is slower than the rotational angular speed of the rotating shaft 23, which prevents strong rubbing at the point of contact between the endless belt 23 and the pulley 7. In this way, the generating efficiency of the alternator is maintained, and the direction of the stress acting on the section of contact between the pulley 7 and the endless belt 23 is constant, preventing slipping to occur between the endless belt 23 and pulley 7, and preventing a decrease in the life of the endless belt 23.
Moreover, in the case of the pulley apparatus with built-in one-way clutch shown in FIG. 4, an attachment protrusion 17 is formed in the circumferential direction around part of the inner peripheral surface on one end in the axial direction of the clutch retainer, and is held between the end surface of the inner ring 11 of the one-way clutch and the end surface (right end in FIG. 4) of the inner bearing race 19 of one of the support bearings 9. Therefore, it is possible to prevent displacement in the axial direction of the clutch retainer 16, and it is possible to cause the clutch retainer 16 to rotate together with the sleeve 8.
In addition, when using the pulley apparatus with built-in one-way clutch, it is possible to prevent sliding contact with the member (such as the outer bearing race 18) that rotates relative to the clutch retainer 16 due to displacement of the clutch retainer 16 in the axial direction, as well as it is possible to prevent heat that is generated due to this sliding contact. Therefore, it is possible to prevent heat degradation of the grease inside the pulley apparatus with built-in one-way clutch as well as prevent heat deformation of the clutch retainer 16.
Also, construction of combining a bearing unit together with a one-way clutch, in which the outer peripheral surface of the inner ring for the one-way clutch or the sleeve is a simple cylindrical surface, and in which the inner peripheral surface of the outer ring of the one-way clutch is a cam surface is disclosed in Japanese Patent Publication No. Jitu Ko Hei 5-42268 and Japanese Patent Publication Toku Kai Hei No. H7-317808.
In the case of Japanese Patent Publication No. Jitu Ko Hei 5-42268, the protrusion that is formed around the outer peripheral surface on the end in the axial direction of the clutch retainer of the one-way clutch is engaged in a groove section that is formed around the inner peripheral surface of the outer ring for the one-way clutch.
In the case of the construction disclosed in Japanese Patent Publication No. Toku Kai Hei 7-317808, a collar section is formed around the outer peripheral surface on the end in the axial direction of the clutch retainer, and held between the outer ring for the one-way clutch and the support bearing, which is a sliding bearing.
With the construction in either of these publications, it is possible to prevent the clutch retainer from displacing in the axial direction in the same way as in the prior art construction shown in FIG. 3.
In the case of the prior art construction, there is a possibility that the following problems may occur. First, in the case of the construction disclosed in Japanese Patent Publication No. Toku Kai Hei 11-22753 and the construction disclosed in Japanese Patent Publication No. Toku Kai Hei 7-317808 and shown in FIG. 4, it is difficult to handle all of the components of the one-way clutch 10 as one body before the one-way clutch 10 is installed in the pulley apparatus.
For example, in the case of the construction disclosed in Japanese Patent Publication No. Toku Kai Hei 11-22753, neither the outer ring 14 nor the inner ring 11 for the one-way clutch are constructed for preventing the clutch retainer 16 from displacing in the axial direction. Therefore, when handling the one-way clutch 10 separately, it is easy for the clutch retainer 16 and the plurality of rollers 15 that are held by the clutch retainer 16 to come out from the outer ring 14 and the inner ring 11 for the one-way clutch.
Also, in the case of the construction disclosed in Japanese Patent Publication No. Toku Kai Hei 7-317808, the sleeve functions as the inner race of the support bearings or the inner ring of the one-way clutch, so it is not possible to handle the one-way clutch separately. Therefore, in the case of the construction described in these publications, assembly work becomes troublesome.
Moreover, the construction disclosed in Japanese Patent Publication No. Jitu Ko Hei 5-42268 and the construction disclosed in Japanese Patent Publication No. Toku Kai Hei 7-317808 is not suitable for use on the alternator pulley. The reason for this is as follows. In the case of the construction described in these publications, the cam surface is formed on the inner peripheral surface of the outer ring of the one-way clutch instead of the outer peripheral surface of the inner ring (or sleeve) of the one-way clutch. The rollers of the one-way clutch are pressed elastically by a plurality of springs toward the section of the cylindrical space between the cam surface and the outer peripheral surface of the inner ring (or sleeve) of the one-way clutch that becomes narrow in the radial direction. Also, when the pulley rotates in a specified direction relative to the sleeve, the rollers are locked, and when the pulley rotates in the opposite direction relative to the sleeve, the rollers are in the overrun state.
However, when the construction disclosed in Japanese Patent Publication No. Jitu Ko Hei 5-42268 or the construction disclosed in Japanese Patent Publication No. Toku Kai Hei 7-317808 is used in the pulley apparatus for driving an auxiliary engine device such as the alternator, the movement of the rollers, due to the centrifugal force acting on the rollers that occurs due to the rotation of crankshaft or alternator rotating shaft, becomes unstable. In other words, the rotational speed of the crankshaft or rotating shaft changes greatly, and so the magnitude of the centrifugal force also changes greatly.
The centrifugal force acting on the rollers in this way presses the rollers against the bottom surfaces of the grooves of the cam surface, and as a result, generates a component force in the direction that causes the rollers to displace along the bottom surface of the grooves. Also, when the rotational speed of the crankshaft or rotating shaft changes in this way, the magnitude of the component force due to the centrifugal force also changes, and the elastic force of the springs required for pressing the rollers is no longer constant.
Therefore, it is not possible to securely obtain a locked state, and during the overrun state, the elastic force applied to each of the rollers becomes too large, and there is a possibility that abnormal heat will be generated due to sliding contact between the rollers and the outer peripheral surface of inner ring of the one-way clutch (or sleeve), or between the rollers and the inner peripheral surface of the outer ring of the one-way clutch.
It is difficult to assemble and use the construction disclosed in Japanese Patent Publication No. Jitu Ko Hei 5-42268 and the construction disclosed in Japanese Patent Publication No. Toku Kai Hei 7-317808 in an auxiliary drive pulley apparatus such as an alternator without the problems described above occurring.
This invention was invented taking the above problems into consideration.
Similar to the prior art construction shown in FIG. 4, the pulley apparatus with built-in one-way clutch of this invention comprises: a sleeve that can be connected and fixed to the tip end of the rotating shaft; a pulley that is located around this sleeve such that it is concentric with the sleeve; a one-way clutch, which is located in the space between the middle section in the axial direction of the outer peripheral surface of the sleeve and the middle section in the axial direction of the inner peripheral surface of the pulley such that it freely transmits rotating power between the pulley and sleeve only when the pulley rotates in a predetermined direction relative to the sleeve; and a pair of support bearings that are located on both sides in the axial direction of the one-way clutch in the space between the outer peripheral surface of the sleeve and the inner peripheral surface of the pulley such that they support the radial load applied to the pulley and make it possible for the sleeve and pulley to rotate freely with respect to each other.
One feature of the pulley apparatus with built-in one-way clutch of this invention is that the one-way clutch is a roller clutch comprising: an outer ring for the one-way clutch that is fitted into and fixed around the inner peripheral surface in the middle section in the axial direction of the pulley; an inner ring for the one-way clutch that is fitted onto and fixed around the outer peripheral surface in the middle section in the axial direction of the sleeve; and a plurality of rollers that are held by a clutch retainer between the outer ring and inner ring for the one-way clutch. The support bearings have inner bearing races that are fitted onto and fixed around the outer peripheral surfaces on both end in the axial direction of the sleeve. Also, the diameter of the inscribed circle of the inner peripheral surface on both ends in the axial direction of the clutch retainer is less than the outer diameter of the end surface in the axial direction of the inner bearing race that faces the clutch retainer.
Another feature of the pulley apparatus with built-in one-way clutch of this invention is that the one-way clutch is a roller clutch comprising: an outer ring for the one-way clutch that is fitted into and fixed around the inner peripheral surface in the middle section in the axial direction of the pulley and has a pair of collar sections that are formed, protruding to the inner-diameter side, on both ends in the axial direction; an inner ring for the one-way clutch that is fitted and fixed around the outer peripheral surface in the middle section in the axial direction of the sleeve, and such that the outer peripheral surface of the inner ring forms a cam surface defined by a plurality of concave grooves that are formed such that the depth in the radial direction becomes larger toward a specified circumferential direction; and a plurality of rollers that are held by a clutch retainer between the outer ring and inner ring for the one-way clutch. Each of the support bearings has an inner bearing race that is fitted onto and fixed around the outer peripheral surfaces closer to both ends in the axial direction of the sleeve.
Also, the inner diameters of the collar sections of the outer ring for the one-way clutch are larger than the outer diameter of the end in the axial direction of the clutch retainer, which is located on the same side as these collars, and the diameter of the inscribed circle on the inner peripheral surface of both ends in the axial direction of the clutch retainer is less than the outer diameter of the end surface in the axial direction of the inner bearing race that faces the clutch retainer.
In the case of the pulley apparatus with built-in one-way clutch of this invention that is constructed as described above, it is possible to regulate the displacement of the clutch retainer of the one-way clutch in the axial direction by the inner bearing races of the support bearings. Therefore, it is possible to prevent the clutch retainer from rubbing against the other components such as the outer ring for the one-way clutch without having to form the clutch retainer into a special shape. Also, it is possible to suppress friction heat that occurs during overrun, so it is possible to prevent heat degradation of the lubrication grease inside the clutch and heat deformation of the components of the clutch.
Furthermore, in the case of this invention, there is a pair of collar sections, protruding to the inner-diameter side, on both ends in the axial direction of the outer ring for the one-way clutch, so before the one-way clutch is installed in the pulley apparatus, the components of the one-way clutch can be handled substantially as one body. Since the one-way clutch can be handled easily, it is possible to improve the ability to install the one-way clutch built-in one-way clutch for an alternator. Also, in the case of this invention, there is a cam surface formed around the outer peripheral surface of the inner ring for the one-way clutch, so during operation, it is possible to stabilize the locked state and overrun state while at the same time suppressing the generation of heat during overrun, even when being used under conditions where the rotational speed changes greatly.